person cleaning area of a womens arm while wearing mask

Our patients are asking about the SARS-CoV-2 vaccine which will be used to prevent COVID-19 as well as the newer types of vaccines, the mRNA. So, I think it’s time for a primer on vaccines.


When our immune system first encounters an invader or ‘antigen’, its response is slow. This is known as the primary response. The body’s soldiers, known as t-cells and b-cells, have to first recognize the invader, become active and start to multiply. The next time, the immune system sees that antigen (i.e. virus), its response is much faster and stronger. We call this the secondary response and it is the basis for vaccines.


There are several types of vaccines:


Live attenuated vaccines take a weakened form of the germ so that they cannot cause illness but the immune system sees what they look like. Vaccines that combat mumps, measles, rubella, chickenpox and shingles are examples of these vaccines. Flumist, the nasal vaccine for the flu, is of this type as well.


Inactivated (killed) vaccines also use the germ we want to protect against, but they are killed. Polio, hepatitis A and rabies are examples of these vaccines.


Toxoid vaccines include only the disease-causing part of the bacteria. The bacteria that cause Diptheria and tetanus produce chemicals known as toxins, which make the body sick. By inactivating these toxins, the body is able to mount an immune response.


Conjugate vaccines take a piece of an invader and attach it to a carrier protein. It’s like taking a recognizable part and presenting it to the immune system on a platter. The body’s cells can recognize the germ much easier this way.


Lastly, the mRNA vaccines. When a virus infects us, it brainwashes our own cells to make multiple copies of itself. mRNA vaccines counter this offence by producing a single protein to recognize the virus and produce a strong secondary response.


There are many ways for vaccines to teach our bodies to fight infection, all without causing disease and thereby saving millions of lives. Take care of yourselves and each other.